The effect of oxygen on wound healing has been extensively studied. Wound healing is dependent upon several processes including proliferation of fibroblasts, collagen synthesis, angiogenesis and re-epithelialization. Many skin sores, ulcers, wounds and burns do not heal properly because there is a severe depletion of oxygen reaching these affected areas due to deterioration of the associated blood microcirculation. Tissue oxygen levels have previously been measured in non-healing wounds to be (5-20 mmHg) as compared to control tissue values of 30-50 mmHg.
Hitherto, many of these wound healing disorders have been treated by various methods of administration of oxygen gas, known as, either through inhalation of the gas in hyperbaric oxygen therapy, or by topical treatment with the gas.
Treatments based on inhalation of oxygen, while considered effective, are complex and entail a risk from the potential harmful effects of prolonged hypoxia.
Numerous wound treatment devices are known that administer oxygen gas topically to wound surfaces. Examples can be found in GB-A-2409412, WO-A-9853778, U.S. Pat. No. 6,179,804, U.S. Pat. No. 4,624,656, U.S. Pat. No. 4,224,941, U.S. Pat. No. 5,662,625, U.S. Pat. No. 5,810,795, FR-A-2656218 and WO-A-9741816. These devices generally comprise an impermeable sheet having a peripheral region for attachment in gas-tight fashion around the wound, for example with adhesive, to form an enclosed chamber over the wound. The devices further comprise a gas inlet for introducing oxygen gas into the chamber above the wound, and optionally an outlet for removal of gas from the chamber. The devices can be operated with a static charge of gaseous oxygen, or with a continuous flow of gaseous oxygen over the wound. It will be appreciated that such devices are relatively bulky and prone to leakage, and can interfere with dressing changes and removal of wound exudates.
U.S. Pat. No. 6,139,876 describes a gelatin with increased oxygen content for use as a topical wound dressing. The gelatin comprises a gelling agent, a solvent, and microbubbles of oxygen in a substantially even distribution with a partial pressure exceeding normal atmospheric pressure, wherein the surface tension of the gelatin is sufficiently high to retain at least a portion of the overpressure of the oxygen throughout a predetermined period of time after having been exposed to an atmospheric environment.
US20020160053 describes an aqueous solution for promoting the growth of tissue cells at wound sites. This solution comprises water containing at least 1 to 500 ppm of active oxygen and 10 to 10000 ppm of halogen ions. The solution is produced by electrolysis of aqueous halide solutions. The active oxygen can include singlet oxygen formed by excitation of triplet oxygen, superoxide formed by reduction of oxygen by a single electron, and hydroxy radical, as well as hypochlorous ions, organic peroxy radicals (ROO.), alkoxy radicals (RO.), and organic hydroperoxides (ROOH). However, the physiological effects of these reactive oxygen species differ from the effect of oxygen gas, and indeed the reactive oxygen species can be deleterious to wound healing.
U.S. Pat. No. 2,005,0125035 describes an active suture having an internal passageway for post-surgical delivery of active fluids. The active fluids may comprise a wide range of medicaments, including oxygen-rich liquids to assist wound healing.